Date and time input and output formats¶

Data unloading¶

When used in data unloading, the options specify the format applied to the dates, times, and timestamps unloaded to the files in specified stage.

The default for all these options is AUTO, meaning Snowflake applies the formatting specified in the following parameters:

• DATE_OUTPUT_FORMAT

• TIME_OUTPUT_FORMAT

• TIMESTAMP_*_OUTPUT_FORMAT (depending on the TIMESTAMP_TYPE_MAPPING setting)

About the elements used in input and output formats¶

In input and output formats that you specify in parameters, file format options, and conversion functions, you can use the elements listed in the table below.

The next sections also use these elements to describe the formats recognized by Snowflake automatically.

Date formats¶

For descriptions of the elements used in the formats below, see About the elements used in input and output formats.

When using AUTO date formatting, dashes and slashes aren’t interchangeable. Slashes imply MM/DD/YYYY format, and dashes imply YYYY-MM-DD format. Strings such as '2019/01/02' or '01-02-2019' aren’t interpreted as you might expect.

Time formats¶

For descriptions of the elements used in the formats below, see About the elements used in input and output formats.

The AM format element allows values with either AM or PM.

When a timezone offset (for example, 0800) occurs immediately after a digit in a time or timestamp string, the timezone offset must start with + or -. The sign prevents ambiguity when the fractional seconds or the time zone offset does not contain the maximum number of allowable digits. For example, without a separator between the last digit of the fractional seconds and the first digit of the timezone, the 1 in the time 04:04:04.321200 could be either the last digit of the fractional seconds (that is, 321 milliseconds) or the first digit of the timezone offset (that is, 12 hours ahead of UTC).

Timestamp formats¶

For descriptions of the elements used in the formats below, see About the elements used in input and output formats.

When a timezone offset (for example, 0800) occurs immediately after a digit in a time or timestamp string, the timezone offset must start with + or -. The sign prevents ambiguity when the fractional seconds or the time zone offset does not contain the maximum number of allowable digits. For example, without a separator between the last digit of the fractional seconds and the first digit of the timezone, the 1 in the time 04:04:04.321200 could be either the last digit of the fractional seconds (that is, 321 milliseconds) or the first digit of the timezone offset (that is, 12 hours ahead of UTC).

SELECT TO_TIMESTAMP('2019-02-28T23:59:59', 'YYYY-MM-DD"T"HH24:MI:SS');

Valid ranges of values for fields¶

The recommended ranges of values for each field are shown below:

Using the correct number of digits with format elements¶

For most fields (year, month, day, hour, minute, and second), the elements (YYYY, MM, DD, and so on) of the format specifier are two or four characters.

The following rules tell you how many digits you should actually specify in the literal values:

• YYYY: You can specify 1, 2, 3, or 4 digits of the year. However, Snowflake recommends specifying 4 digits. If necessary, prepend leading zeros. For example, the year 536 A.D. is 0536.

• YY: Specify 1 or 2 digits of the year. However, Snowflake recommends specifying 2 digits. If necessary, prepend a leading zero.

• MM: Specify one or two digits. For example, January can be represented as 01 or 1. Snowflake recommends using two digits.

• DD: Specify one or two digits. Snowflake recommends using two digits.

• HH12 and HH24: Specify one or two digits. Snowflake recommends using two digits.

• MI: Specify one or two digits. Snowflake recommends using two digits.

• SS: Specify one or two digits. Snowflake recommends using two digits.

• FF9: Specify between 1 and 9 digits (inclusive). Snowflake recommends specifying the number of actual significant digits. Trailing zeros aren’t required.

• TZH: Specify one or two digits. Snowflake recommends using two digits.

• TZM: Specify one or two digits. Snowflake recommends using two digits.

For all fields (other than fractional seconds), Snowflake recommends specifying the maximum number of digits. Use leading zeros if necessary. For example, 0001-02-03 04:05:06 -07:00 follows the recommended format.

For fractional seconds, trailing zeros are optional. In general, it is considered good practice to specify only the number of digits that are reliable and meaningful. For example, if a time measurement is accurate to three decimal places (milliseconds), then specifying it as nine digits (for example, .123000000) might be misleading.

Whitespace in values and format specifiers¶

Snowflake enforces matching whitespace in some, but not all, situations. For example, the following statement generates an error because there is no space between the days and the hours in the specified value, but there is a space between DD and HH in the format specifier:

SELECT TO_TIMESTAMP('2019-02-2823:59:59 -07:00', 'YYYY-MM-DD HH24:MI:SS TZH:TZM');

However, the following statement doesn’t generate an error, even though the value contains a whitespace where the specifier doesn’t:

SELECT TO_TIMESTAMP('2019-02-28 23:59:59.000000000 -07:00', 'YYYY-MM-DDHH24:MI:SS.FF TZH:TZM');

The reason for the difference is that in the former case, the values would be ambiguous if the fields aren’t all at their maximum width. For example, 213 could be interpreted as 2 days and 13 hours, or as 21 days and 3 hours. However, DDHH is unambiguously the same as DD HH (other than the whitespace).

Context dependency¶

Not all restrictions are enforced equally in all contexts. For example, some expressions might roll over February 31, while others might not.

Summary of best practices for specifying the format¶

These best practices minimize ambiguities and other potential issues in past, current, and projected future versions of Snowflake:

• Be aware of the dangers of mixing data from sources that use different formats (for example, of mixing data that follows the common U.S. format MM-DD-YYYY and the common European format DD-MM-YYYY).

• Specify the maximum number of digits for each field (except fractional seconds). For example, use four-digit years, specifying leading zeros if necessary.

• Specify a blank or the letter T between the date and time in a timestamp.

• Make sure whitespace (and the optional T separator between the date and time) are the same in values and in the format specifier.

• Use interval arithmetic if you need the equivalent of rollover.

• Be careful when using AUTO formatting. When possible, specify the format, and ensure that values always match the specified format.

• Specify the format in the command, because it is safer than specifying the format outside the command, for example in a parameter such as DATE_INPUT_FORMAT. (See below.)

• When moving scripts from one environment to another, ensure that date-related parameters, such as DATE_INPUT_FORMAT, are the same in the new environment as they were in the old environment (assuming that the values are also in the same format).